linux-kernel - Re: multi-second application stall in open()

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Message-ID: <20120622204207.GA22063@redhat.com>
Date:	Fri, 22 Jun 2012 16:42:07 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Josh Hunt <joshhunt00@...il.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	tj@...nel.org
Subject: Re: multi-second application stall in open()

On Fri, Jun 22, 2012 at 03:22:01PM -0500, Josh Hunt wrote:

[..]
> It looks like my statement about busy_queues isn't entirely accurate.
> I'm seeing this later on in the trace:

Yes it is being called some times. But it is interesting to see that in
the instance you pasted in last mail, we did not see "schedule_dispatch"
message.  Are you sure that other requests were queued at that point of
time and there were busy_queues? You can try printing cfqd->rq_queued
to verify that.

Also put some message in cfq_select_queue() to see why it did not select
a new queue before the stall.

Thanks
Vivek
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